Several branches of the potential outcome causal inference literature have discussed the merits of blocking versus complete randomization. Some have concluded it can never hurt the precision of estimates, and some have concluded it can hurt. In this article, we reconcile these apparently conflicting views, give a more thorough discussion of what…

Group design research studies can provide evidence to draw conclusions about "what works," "for whom," and "under what conditions" in special education. The quality indicators introduced by Gersten and colleagues (2005) have contributed to increased rigor in group design research, which has provided substantial…

Randomized experiments are often seen as the "gold standard" for causal research. Despite the fact that experiments use random assignment to treatment conditions, units are seldom selected into the experiment using probability sampling. Very little research on experimental design has focused on how to make generalizations to well-defined…

Adolescent clinical and subclinical depression has a significant negative impact on adolescents well being, school performance and consequently produces maladaptive outcomes in terms of subsequent education and occupational functioning. This research is a part of a larger research project with a focus on clinical and subclinical depression during…

Using exogenous characteristics to identify endogenous subgroups, the approach discussed in this method note creates symmetric subsets within treatment and control groups, allowing the analysis to take advantage of an experimental design. In order to maintain treatment--control symmetry, however, prior work has posited that it is necessary to use…

This research aims to analyse the Effect of Scrolling and page by page moving Static Texts on Comprehension of Screen Reading of 4th grade students. The sample was composed of 46 students of 4th grade students of a elementary school in Kirsehir Central Province. The classrooms of the participants were selected by random sampling method and…

The potential for music programs to promote psychosocial wellbeing in mainstream schools is recognised in both policy and research literature. Despite this recognition, there is a dearth of consistent research evidence supporting this link. Authors attribute this lack of consistent evidence to limitations in the areas of research design and…

This paper provides practical guidance for researchers who are designing and analyzing studies that randomize schools--which comprise three levels of clustering (students in classrooms in schools)--to measure intervention effects on student academic outcomes when information on the middle level (classrooms) is missing. This situation arises…

Background: Recruiting schools into a matched-pair randomized control trial (MP-RCT) to evaluate the efficacy of a school-level prevention program presents challenges for researchers. We considered which of 2 procedures would be most effective for recruiting schools into the study and assigning them to conditions. In 1 procedure (recruit and…

Examined Type I error rates and power for four tests for treatment control studies in which a larger treatment mean may be accompanied by a larger treatment variance and examined these aspects of the independent samples "t" test and the Welch test. Evaluated each test and suggested conditions for the use of each approach. (SLD)

Flexibility in evaluative research design does not necessitate the abandonment of randomly constructed comparison groups. Three designs are reviewed which provide at least the option of randomization while maintaining great flexibility. The strengths and weaknesses of the designs are discussed. (Author)

A review and meta-analysis were made of placebo control groups in educational experiments. In all, 125 studies were clustered into procedures that included (1) explicit manipulation of attentional elements; (2) explicit description of the placebo activity plus implied reference to attention; and (3) exclusive reference to the activity. (SLD)

A meta-analysis was conducted on 44 educational studies that used either a (labelled) Hawthorne control group, a manipulation of Hawthorne effects, or a group designed to control for the Hawthorne effect. The sample included published journal articles, ERIC documents or unpublished papers, and dissertations. The studies were coded on 20 variables,…

A solution is proposed for analysis of variance procedures with missing cells, such as may occur when a control group is not assigned to any of the rows or columns of the various experimental groups. Mathematical models for two-way design are presented which define several variables; as well as row effect, column effect, and row and column…

This paper identifies methodological and practical problems in studies of child maltreatment, including developing classification schemes for multiple forms of maltreatment; distinguishing between chronic maltreatment and isolated incidents; choosing criteria for selecting comparison groups; determining whether comparison groups have experienced…